南极海冰与气候

在极区,海冰的形成在海洋上部和大气下部之间构成了新的交界面,改变了大洋表面的辐射平衡和能量平衡,隔离了海洋与大气之间的热交换和水汽交换;海冰冻融过程影响着大洋温、盐流的形成和强度;海冰对南大洋和南极大陆气象、气候有重要的影响,在气候环境系统中起着重要的作用。南极海冰作用区约占南半球雪冰作用区面积的58%,约占地球表面积的3.58%。其中,一年生海冰约占南极海冰区分布面积的83%;其分布面积从夏末2月份最小时的3×106 km2左右,到9月份冬末最大时的18×106 km2左右,一年中季节变化幅度可达15×106 km2,季节变化率>500%。海冰分布区域的年际变化较大。南极海冰区是影响季节和年际全球气候环境变化的重要区域。当前,国际南极海冰与气候研究的核心问题是海冰物理过程和在海冰区的海洋—大气相互作用。结合目前承担的研究课题,对国际南极海冰与气候研究的前沿动态和相关的国际计划进行了综述。     

基于CryoSat-2卫星测高数据分析南极海冰厚度的时空变化

利用卫星测高数据能够获取大尺度、长时序的海冰厚度信息。相较于北极,目前南极海冰厚度特别是近期变化信息仍很缺乏。基于2013-2018年的CryoSat-2卫星测高数据,采用最低点高程法和静力平衡方程模型反演了近6年逐月平均海冰厚度并分析其时空变化规律。结果表明：2013-2018年南极海冰厚度整体呈现先上升后下降的趋势,其中,2014-2017年年平均海冰厚度表现为快速变薄。南极较厚的海冰集中在威德尔海西南海域,最大值出现在该海域2014年的7月（6.27 m）。年平均海冰厚度在2017年达到最低值。南极海冰厚度的时空变化研究可为深入研究海冰变化与全球变化的关系提供参考。     

南极海冰异常对南半球冬春季大气环流影响的年代际变化

南极海冰异常是影响南半球大气环流变化的一个重要因素。南极海冰变率的主要模态被称为南极海冰偶极子(Antarctic Dipole, ADP),具体表现为南极半岛两侧海冰的反相变化。ADP的出现受到厄尔尼诺-南方涛动事件的强烈影响,而过去的研究显示,厄尔尼诺在2000年后由东部型转到中部型,伴随着该转变,南极海冰的异常模态及其对南半球大气环流的影响也发生了年代际变化。通过对前期的南极海冰异常与滞后的南半球冬春季位势高度异常进行最大协方差分析,发现南半球冬季至春季持续性的正位相ADP,在1979—1999年间与南半球春季的负位相南半球环状模(Southern Hemisphere Annular Mode,SAM)显著关联,但在2000—2021年间该相关性较弱,转变为南半球秋季的三极型海冰异常与后期冬季的SAM显著相关。动力诊断证明,ADP及三极型海冰异常均能通过引发高频瞬变涡旋的变化,激发并维持SAM型大气环流异常。     

南极海冰和陆架冰的时空变化动态

利用美国冰中心和雪冰中心提供的海冰资料和我国南极考察现场的海冰观测资料, 对南极海冰的长期变化进行了研究.结果表明: 20世纪70年代后期是多冰期; 80年代是少冰期; 90年代南极海冰属于上升趋势, 后期偏多; 区域性变化差别大, 东南极海冰偏多, 西南极海冰即南极半岛两侧特别是威德尔海(Weddell Sea)区和别林斯高晋海(Bellingshausen Sea)的冰明显偏少.东南极和西南极海冰的变化趋势总是反相的.90年代后期普里兹湾的海冰明显偏多, 南极大陆陆架冰外缘线总体没有明显的收缩, 有崩解也有再生的自然变化现象.西南极威德尔海的龙尼冰架(Ronne Ice Shelf)和罗斯海冰架(Ross Ice Shelf)东部崩解和收缩趋势明显, 东南极的冰架也有崩解和收缩, 但没有西南极明显.陆架冰崩解向海洋输送的冰山对全球海平面升高有一定的影响.目前, 南极冰盖断裂崩解形成的冰山, 向海洋输入的水量可使全球海平面上升约14 mm.南极海冰没有随着全球气候温暖化而明显减少, 而是按照东南极和西南极反相的变化规律进行周期性的变化、调整和制约.     

南极海冰涛动及其对东亚季风和我国夏季降水的可能影响

利用NCEP 1973-2002年逐月南极海冰密集度格点资料,定义了具有跷跷板式变化规律的南极海冰涛动指数,分析了冬季南极海冰涛动指数与我国夏季降水及东亚季风爆发时间的关系.结果显示:南极海冰涛动指数与同期南极海冰密集度相关系数超过5%信度的格点数占南极海冰格点数的1/3,表明定义南极海冰涛动指数能够代表南极地区1/3海冰的变化区域.冬季南极海冰涛动指数和我国汛期(6-8月)降水距平百分比相关显著,正相关主要在长江流域及其以南地区,长江流域以北为负相关,相关系数均超过5%的信度.当冬季南极海冰涛动指数为负值时,南海季风爆发早,概率为11/14=79%;为正值时南海季风爆发晚,概率为12/15=80%.通过讨论冬季南极海冰涛动指数影响我国季风降水的可能过程,给出了概念模型.     

电磁感应技术在南极海冰厚度探测中的应用

介绍一种能够高效探测海冰厚度的电磁感应方法及其在南极考察中的应用。该技术方法针对海冰和海水的电特性,利用电磁场原理精确探测仪器至冰水交界面的距离,以实现海冰厚度的测定。通过电磁感应(EM)仪观测的视电导率与同点位钻孔测量数据对比分析,获得视电导率与海冰厚度的换算关系式,通过对用该关系式计算出的海冰厚度进行验证,表明电磁感应技术能够获得可靠的海冰厚度数据。对探测剖面的海冰厚度统计表明,2005—2006年夏季南极内拉峡湾内海冰以平整冰为主,其厚度为0.8~1.4 m。     

ENSO循环过程与南极海冰变化

应用1951-2001年ENSO特征指数(NINO1+2、NINO3、NINO4、NINO3.4、SOI)和1973-1998年南极海冰北界范围以及1950-2001年SODA海洋温度资料,分析探讨了ENSO循环过程与南极海冰之间的关系,研究了南大洋和太平洋海表温度与南极海冰之间的内在联系。结果表明,南极海冰变化与ENSO循环过程存在一定联系,特别是东南极海冰的变化与ENSO循环过程较为密切。这种遥相关关系表明,ENSO循环过程不仅与热带海洋自身的海 气相互作用存在密切关系,而且与南极海冰之间也存在一定的联系。当东南极海冰范围出现异常增大和减小时,在时滞一年之后,NINO循环指数将出现减弱和加强,而南方涛动指数将出现加强和减弱。这种相关关系的机制是通过大洋环流这一载体将异常海温向北输送来实现的。南极海冰范围的异常增加或减少,会直接影响南极绕极流的冷暖结构进而影响经向水体输送的异常,从而导致热带和副热带太平洋上层海温场的异常变化,对ElNino和LaNina事件的发生起到推动作用。     

南极大陆东部戴维斯站地区海冰观测

1981年1—12月,笔者在南极戴维斯(Davis)站工作期间,对站区沿海海冰的形成和破裂过程以及海冰的一些物理性质作了观察,并且从3月20日至11月30日,和澳大利亚考察队员一起,测量了海冰厚度和冰下水温(每周一次)。最近笔者又查阅了南极大陆东部沿海站区有关海冰的一些资料并进行了比较。现将这些观测资料介绍于后,供我国海冰和南极研究者参考。     

南极沿岸固定冰观测与研究述评

南极固定冰的变化能够直接反映南极的局地气候变率,因此是数值模式验证的理想载体,对固定冰的观测研究结论也能用于评估南极海冰的年际变化。现今国际上对南极固定冰的观测和研究日渐丰富和深入,并逐渐形成了由多个国家参加的联合观测网。就海冰厚度、冰芯结构、表面辐射收支等现场测量和相机、卫星等遥感观测方面,总结了目前国内外南极固定冰观测的技术手段和研究进展,并分析了不同空间尺度上的南极固定冰年际变化特征。对南极固定冰观测研究目前存在的问题和未来的发展方向进行了探讨。     

大气、海洋与固体地球的能量交换

通过对南极气温资料、南极臭氧资料、环南极海冰资料、太平洋海温资料、地球自转速度变化资料、厄尔尼诺和拉尼娜资料的模拟验证，发现厄尔尼诺事件发生与德雷克海峡海冰减少在时间上有一一对应关系。南极半岛海冰减少是太平洋环流速度减慢的原因，德雷克海峡的海冰起重要作用。大气、海洋与固体地球的角动量交换在南、北半球有不同的形式。强震起源于海平面振荡。     

The East Antarctic sea ice zone: Ice characteristics and drift

Results from studies of the surface energy balance and the ocean structure in the presence of fast ice near Mawson on the Antarctic coast are used to illustrate the important ways in which sea ice interacts with the ocean and atmosphere. Away from the coast, ship and drifting buoy observations are used to characterize the E Antarctic sea ice zone in a study area between 60° E and 120° E and S of 61° S. Divergent drift over most of the region plays a dominant role in expanding the ice extent in autumn and in determining the characteristics of the pack. Much of the sea ice in the region is young thin ice which forms in leads and polynyas, and in late spring in the study area, the ice thickness averaged over the total ocean surface within the ice edge less than 0.4 m. Even in winter the majority of ice floes off E Antarctica are probably less than 1 m thick.     

国际南极冰盖与海平面变化研究述评

海平面上升是全球变暖的主要后果之一。尽管有少数冰川学家认为,气候变暖并不能确保雪积累量的显著增加,同时可能出现冰流的突然变化,因此南极冰盖在未来海平面变化中的作用存在很大的不确定性。但近几十年来南极半岛气温的急剧上升,已使大量的冰架崩解。冰架崩解并不对海平面产生真正的影响,但反映出南极洲气候与冰川存在急剧变化的可能。     

南极和北极地区在全球变化中的作用研究

近半个世纪的调查基本揭示了极地在地球系统中的作用。两极保持了世界 99%的冰川 ,相当于全球淡水的 78% ,全部融化将使地球海平面上升 70m。极区又是世界气候系统中最活泼的组成 ,通过其冰盖、大气和周围海域的强烈耦合过程而影响全球。同时 ,南极上空臭氧空洞的出现 ,北极地区冻土带的北移等都表明全球变化也在明显地影响着两极。中国 2 0年来对南极的考察过程中 ,建立两个南极科学考察站 ,拥有极地考察破冰船 ,1999年开展了中国首次北极科学考察 ,对南北极的区域特征及其在全球变化中的作用提出了新的认识。     

Volume of Antarctic Ice at the Last Glacial Maximum, and its impact on global sea level change

The volume of Antarctic ice at the Last Glacial Maximum is a key factor for calculating the past contribution of melting ice sheets to Late Pleistocene global sea level change. At present, there are large uncertainties in our knowledge of the extent and thickness of the formerly expanded Antarctic ice sheets, and in the timing of their release as meltwater into the world’s oceans. This paper reviews the four main approaches to determining former Antarctic ice volume, namely glacial geology, glacio-isostatic studies, glaciological modelling, and ice core analysis and attempts to reconcile these to give a ‘best estimate’ for ice volume. In the Ross Sea there was a major expansion of grounded ice at the Last Glacial Maximum, accounting for 2.3–3.2 m of global sea level. At some time in the Weddell Sea a large grounded ice sheet corresponding to c. 2.7 m of global sea level extended to the shelf break. However, this ice expansion has not yet been confidently dated and may not relate to the Last Glacial Maximum. Around East Antarctica there was thickening and advance offshore of ice in coastal regions. Ice core evidence suggests that the interior of East Antarctica was either close to its present elevation or thinner during the last glacial so the effect of East Antarctica on sea level depends on the net balance between marginal thickening and interior thinning. Suggested East Antarctic contributions vary from a 3–5.5 m lowering to a 0.64 m rise in global sea level. The Antarctic Peninsula ice sheet thickened and extended offshore at the Last Glacial Maximum, with a sea level equivalent contribution of c. 1.7 m. Thus, the Antarctic ice sheets accounted for between 6.1 and 13.1 m of global sea level fall at the Last Glacial Maximum. This is substantially less than has been suggested by most previous studies but the maximum figure matches well with one modelling estimate. The timing of Antarctic deglaciation is not well known. In the Ross Sea, terrestrial evidence suggests deglaciation may have begun at c. 13,000 yr BP¹ but that grounded ice persisted until c. 6,500 yr BP. Marine evidence suggests the western Ross Sea was deglaciated by c. 11,500 yr BP. Deglaciation of the Weddell Sea is poorly constrained. Grounded ice in the northern Antarctic Peninsula had retreated by c. 13,000 yr BP, and further south deglaciation occurred sometime prior to c. 6,000 yr BP. Many parts of coastal East Antarctica apparently escaped glaciation at the LGM, but in those areas that were ice-covered deglaciation was underway by 10,000 yr BP. With existing data, the timing of deglaciation shows no firm relation to northern hemisphere-driven sea level rise. This is probably due partly to lack of Antarctic dating evidence but also to the combined influence of several forcing mechanisms acting during deglaciation.     

基于IceBridge数据的南极别林斯高晋海的海冰厚度研究

海冰变化与全球气候、 生态系统和人类活动密切相关, 海冰厚度是海冰变化研究的重要参数之一。全面立体高精度观测海冰厚度的最有效手段是航空遥感, 而冰桥计划（IceBridge）是当前南北极最大的航空遥感工程。基于2009 - 2014年冰桥计划的激光雷达高程数据和数字测图系统相机光学影像对南极别林斯高晋海的海冰厚度进行研究, 并结合降雪量等气象数据探讨该区域海冰厚度变化的原因。研究发现该海域的海冰厚度在2009 - 2014年间整体呈微弱增长趋势（0.07 m·a^-1）, 但是在95%置信水平下不具有显著性。2009 - 2011年呈现先增加后减少的大幅度变化, 其中2010年达到极大值2.42 m, 之后开始缓慢增加。海冰厚度的年际变化与降雪和近地表温度等气象要素相关, 二者相比较而言降雪为主要影响因素。     

气候系统内极区热汇与热带海洋热源之间的相互作用(英)

The anomalous change of two polar sea ice and tropical ocean SST is a very important index for global climate monitoring and prediction. In this paper, the wave resonance principle is used to calculate month by month running cross couple correlation coefficient time series between sea ice in different sea area of two Polars, as well as between them and five elements of E1 Nino events, to analyze their variation features, and to find out their resonance periods. The resonance period of two waves is just the strongest interaction period.Some results are concluded as follows. 1) The Arctic sea ice to the Pacific-side (NPI1) and Atlantic-side (NP12) show a strong positive-negative feedback impact each other to the Antarctic Ross Sea ice (SPI2) with equal intensity. 2) Both NPI1 and NPI2 give a strong positive and negative feedback to the Antarctic Wedded Sea ice (SPI3) while it is rather weak in convercse status. It means that, the Arctic sea ice plays a leading and controlling role on the Wedded Sea ice. 3) SST of Nino 4 area in thecentral equatorial Pacific has a best resonance period with SPI2 with cycle period of 132 months. It closely relates to quasi-11 years oscillation period of both SST of Nino 4 area and SPI2. SST of Nino 4 has also a resonance period to SPI3 with cycle of 61 months. There also exist strong interaction periods between the Antarctic sea ice and other elements of ENSO event but weaker than SST of Nino 4 area.     

Coastal Ecological Risk Assessment: Its Research Progress and Prospect

Coastal areas are located in marine-terrestrial interlaced zone. With their unique geographical positions, the coastal ecological risk assessment has both the complexity of regional ecological risk assessment and its own particularity. In recent years, due to the coastal economic development and the deterioration of ecological environment, coastal ecological risk has received more and more attention, but there are still lacking in further systematic study about the coastal ecological risk assessment. With the summary and analysis of the existing research results from home and abroad, based on land-ocean interaction plan and full consideration of the uniqueness, regionalism and complexity of the coastal zone environment, this paper made scientific conclusion on the definition of the coastal ecological risk assessment concept and its components from risk source, habitat and risk suffer-the three basic elements. Moreover, from risk source, risk suffer and comprehensive evaluation-the three aspects, it discussed in detail the related research topics, progress as well as main conclusions. Then, it analysed the characteristics and evaluation methods, and put forward the framework model of coastal ecological risk assessment. Finally, it analysed and proposed the existing deficiencies and future research direction, providing new ideas for future research on coastal ecological risk assessment.     

Methodological study of coastal geological hazard assessment based on GIS

The current researches on risk assessment of geological disasters mainly focus on unexpected disasters such as collapses, landslides and mud-rock flows etc. As the convergence zone of land and sea, coastal zone is the most active and complex area of interactions of lithosphere, hydrosphere, atmosphere, biosphere and anthroposphere. The ecological environment of coastal zone is very fragile, so further systematical research on coastal geological hazard assessment and prevention is in urgent need. The author begins with the definition and research contents and selects three typical coastal geological disasters, namely, the seawater intrusion, coastline change and sea-level rise as the objects of study. The systematic analysis and study on assessment system and methods are conducted, hazard assessment factors are selected, and a completely set of coastal disaster assessment system is established based on the technique of GIS. We took Bao’an District of Shenzhen City as an example and carried out a case study.